The present invention relates to a method for communicating data in a remote tire pressure monitoring system.
Remote tire pressure monitoring systems have been developed using radio technology for providing centralized tire pressure information to an operator of a vehicle. Such systems typically include a plurality of sending units or transmitters associated with the tires of a vehicle, such as an automobile, truck or other wheeled vehicle along with a receiving unit. The transmitters measure a tire characteristic such as tire air pressure, and communicate data corresponding to the tire characteristic to the receiver. The receiver takes some action in response to the data, such as providing an alarm or providing a display indicative of the tire characteristic, for the operator of the vehicle.
One problem evident in such a system is clashing of data at the receiver. If two transmitters transmit data at the same time, a clash can occur, in which case the receiver is unable to reliably decode the two transmissions. Any overlap of two transmissions from sending units can prevent reception of data from both sending units.
One known solution involves interrupting transmission of data during selected repeating time periods at each transmitter. The total transmission time is divided into a number of sections, such as ten. During selected sections, for example, two of the ten, transmission is suspended to provide a quiet time when data from other sending units may be transmitted and received successfully. If the quiet times of three of four sending units align during a time when the fourth sending unit is transmitting, no clash will occur. If two transmissions from the same sending unit are decoded and are identical, the data is considered valid and reliable.
While this technique has been acceptable, it would be advantageous to further limit clashing to more reliably and more quickly communicate tire characteristic information to the vehicle operator. Accordingly, there is a need for an improved method and apparatus for transmitting data in a remote tire pressure monitoring system which reduces clashing of data.
The present invention is directed to a method for transmitting data in a remote tire pressure monitoring system. One embodiment of the system includes transmitters located at each tire of a vehicle and a receiver mounted on the vehicle.
By way of introduction, the method includes collecting data on a tire characteristic at tires of a vehicle. The data are formatted and transmitted by the transmitter according to a predefined protocol. In one embodiment, each transmitter sends the data during a sequence of aperiodic time windows. Because the time windows are aperiodic, the likelihood of simultaneous or overlapping transmission by two or more transmitters is reduced. In another embodiment, each transmitter waits a variable time delay before beginning its transmission of data. Because the transmitters begin transmitting at differing times, the likelihood of overlapping transmission by two or more transmitters is reduced.
The foregoing description of the present invention has been provided only by way of introduction. Nothing in this section should be taken as a limitation on the following claims, which define the scope of the invention.